DETECT-AGING blind prediction contest: a benchmark for structural health monitoring of masonry buildings

The installation of monitoring systems on buildings allows analyzing variations in structural parameters over time, creating room for detection of damage. Structural Health Monitoring (SHM) systems have the potential to support pro-active risk management, where structural interventions are planned if specific thresholds related to target performance losses are achieved. DETECT-AGING is a research project of relevant national interest that was funded by the Italian Ministry of University and Research (MUR) through the PRIN 2017 programme. The project started in September 2019 and involves the universities of Bologna, Genova, Napoli Federico II, and Perugia. The main goal of the project is to develop a new analytical-instrumental approach aimed at the quantitative assessment of the effects of aging and material degradation on structural safety of cultural heritage, with special focus on masonry structures. Based on a combined use of structural models and health monitoring systems, indications and operational tools will be provided for the identification and quantification of structural damage, supporting the management of built cultural heritage. To this purpose, a two-storey masonry building, having a single room with a vault at the first floor and a timber roof, was built with the aim of being monitored and progressively and will be damaged during the project. It is equipped with a hybrid SHM system managed by the University of Perugia, which is based on both vibration and strain measurements. The present paper illustrates the main features of the case-study building and presents the results of the experimental program aimed at characterizing the mechanical properties of masonry the materials used. The final part of the paper presents a blind prediction contest based on prediction of modal features of the building in different damaged configurations

Low unit strength masonry: computational modelling approaches

Masonry is characterized by the large variability of its components. Parameters like strength, bond and workmanship defects strongly influence the performance of the overall structure. The applicability of different computational modelling approaches to assess the structural behaviour of masonry has been studied. Two of the most relevant computational modelling approaches have been considered namely: finite element method (FEM) and distinct element method (DEM). In order to validate the numerical outcomes, comparisons with the experimental results have been undertaken. The aim of this paper is to contribute to the knowledge and selection of a suitable modelling approach for modelling low unit strength masonry structures. The results showed that in the case of low unit strength masonry, FEM is a more suitable approach to use. In fact, since in the considered case, the block is the weak component, it is not possible to assume the brick units as a rigid block. Therefore an accurate plasticity and cracking model for the brick is required

Shake-table testing of a stone masonry building aggregate: overview of blind prediction study

City centres of Europe are often composed of unreinforced masonry structural aggregates, whose seismic response is challenging to predict. To advance the state of the art on the seismic response of these aggregates, the Adjacent Interacting Masonry Structures (AIMS) subproject from Horizon 2020 project Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe (SERA) provides shake-table test data of a two-unit, double-leaf stone masonry aggregate subjected to two horizontal components of dynamic excitation. A blind prediction was organized with participants from academia and industry to test modelling approaches and assumptions and to learn about the extent of uncertainty in modelling for such masonry aggregates. The participants were provided with the full set of material and geometrical data, construction details and original seismic input and asked to predict prior to the test the expected seismic response in terms of damage mechanisms, base-shear forces, and roof displacements. The modelling approaches used differ significantly in the level of detail and the modelling assumptions. This paper provides an overview of the adopted modelling approaches and their subsequent predictions. It further discusses the range of assumptions made when modelling masonry walls, floors and connections, and aims at discovering how the common solutions regarding modelling masonry in general, and masonry aggregates in particular, affect the results. The results are evaluated both in terms of damage mechanisms, base shear forces, displacements and interface openings in both directions, and then compared with the experimental results. The modelling approaches featuring Discrete Element Method (DEM) led to the best predictions in terms of displacements, while a submission using rigid block limit analysis led to the best prediction in terms of damage mechanisms. Large coefficients of variation of predicted displacements and general underestimation of displacements in comparison with experimental results, except for DEM models, highlight the need for further consensus building on suitable modelling assumptions for such masonry aggregates

Deformability of base connections in shotcreted concrete sandwich load bearing perforated walls

Fast construction of structural walls made of reinforced concrete for buildings or industrial warehouses in single panel is a cost-effective system in terms of both the quality of construction and the economy. Anti-seismic constructions can be built with additional reduction of heat dispersion and noise attenuation. In this study the structural system is composed of a factory produced corrugated panel of polystyrene covered on both sides by an electro-welded zinc coated mesh of galvanized steel and shotcreted concrete poured to build the vertical structural walls. This system allows economic savings compared to the traditional systems; however, deformability of the base connections can alter significantly the structural behaviour and seismic response. This study deals with both experimental tests on a real scale structure and numerical simulations, with the goal to provide an efficient formulation to model the deformability of base connections in such sandwich concrete structures, while the materials are modelled either linear elastic or nonlinear

Effect of fiber-to-matrix bond on the performance of inorganic matrix composites

The strengthening of masonry structures is nowadays performed by means of high-strength fibers embedded in inorganic matrix (FRCM) where lime or cement-based matrix is used instead of epoxy adhesive to reduce debonding issues between substrate and matrix. However, some sliding phenomena and cohesive failures between fibers and the matrix mortar can occur. The paper examines the effect on the FRCM efficiency of the mechanical properties of fiber and matrix and potential geometrical defects, which are possible in real field applications or in qualification tests. The model application to simulate bond tests on typical PBO-FRCM and Glass-FRCM allowed to analyse slips as well as normal and shear stresses both in the bundle and in the matrix constituting the FRCM, for different defects due to application issues. The result of numerical simulations seems to interpret well the results of the qualification tests with a multi-bundle effect that justifies their scatter. The approach can be applied by varying main mechanical properties of the materials (e.g. elastic modulus, fiber cross section, bond properties) to consider their intrinsic variability in the assessment of the performance of the FRCM system or by changing the type of materials (i.e. mortar and fibre) to optimize the FRCM system